- Re-apply 52748 and friends with fix. GetConstantStringInfo() returns an empty string for ConstantAggregateZero case which surprises selectiondag.

- Correctly handle memcpy from constant string which is zero-initialized.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52891 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index d45eb99d93..5d75489d14 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9973,8 +9973,8 @@ static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI,
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(CI)) {
     // Instead of loading constant c string, use corresponding integer value
     // directly if string length is small enough.
-    const std::string &Str = CE->getOperand(0)->getStringValue();
-    if (!Str.empty()) {
+    std::string Str;
+    if (GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) {
       unsigned len = Str.length();
       const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
       unsigned numBits = Ty->getPrimitiveSizeInBits();